Endothelium-derived relaxing factor (EDRF) is a labile humoral agent which is part of a cascade of interacting agents involved in the relaxation of vascular smooth muscle. EDRF is thus important in the control of vascular resistance to blood flow and in the control of blood pressure. Some vasodilators act by causing EDRF to be released from endothelial cells. (See Furchgott, Ann.Rev.Pharmacol.Toxicol. 24, 175-197, 1984.) Recently, Palmer et al., have shown that EDRF is identical to the simple molecule, nitric oxide, NO. (Nature 317, 524-526, 1987.) It has been hypothesized for years that many nitrovasodilators that mimic the effect of EDRF, like glyceryl trinitrate, amyl nitrite, NaNO.sub.2 and sodium nitroprusside (SNP), do so by virtue of their conversion to a common moiety, namely NO, which is also a vasodilator. (See Kruszyna et al., Tox.& Appl. Pharmacol., 91, 429-438, 1987; Ignarro, FASEB J. 3, 31-36, 1989 and Ignarro et al., J. Pharmacol. Exper. Theraputics 218(3), 739-749, 1981.) It has now been discovered that a class of compounds of the structure: ##STR2## wherein A is a secondary amino group, are potent antihypertensives and thus are useful for treating cardiovascular disorders in which lowering the blood pressure has a beneficial result. It is believed that these compounds function by releasing NO in the blood after injection; however the invention should not be limited by this hypothesis. While these compounds are, for the most part, known, there is no suggestion in the prior art that they are anti-hypertensive, indeed, there is no suggestion in the prior art that these compounds have any pharmaceutical use. They are described by Drago in "Free Radicals in Inorganic Chemistry", Number 36, Advances in Chemistry Series, American Chemical Society, Wash. DC, 1962, pages 143-149 and Drago et al. J. Amer. Chem. Soc. 83, 1819-1822, 1961. These two articles by Drago are incorporated by reference, in their entirety. The references are of a theoretical nature and mention no utility whatsoever. Reilly, U.S. Pat. No. 3,153,094, discloses these compounds on columns 11-13, but does not teach any biological activity.